Method of laminating rubber hydrochloride films



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METHOD OF LAMINATNG RUBBER HYDROCHLORIDE FILMS Filed-April 16, 1941 Hy. 4 www' James E'Swyaer sm, /WM

'Pmmd 70a. 12, i943 METHOD OF LAMINATING RUBBER HYDBOCHLORIDE FILMS James E. Snyder, Akron, Ohio, assignor to Wingfoot' Corporation, Akro of Delaware lApplication April 16, 1941, Serial No. 388,715

n, Ohio, a corporation li Claim. (g'Cl. 154-2) This invention relates to the formation of a` new rubber hydrochloride nlm. A

For sometime considerable quantities of process cheese have been packaged in rubber hydrochloride nlm. The usual untreated rubber hydrochloride nlm has not been entirely satisfactory for this purpose. The housewife is used to cutting off slices of the cheeseas 'required and keeping the block from which slices have been cutin cold storage. The usual untreated nlm does not adhere tightly to the-cheese and after a slice has been cut from the block of cheese, air enters between the cheese `and the wrapper and mold may form on the cheese.` Also this poor cling causes trouble in slicing.

If a waxy substance is added to the nlm in an amount in excess of that required to saturate the nlm, so that there is a bloom of the waxy substance on the surface of the nlm, the film adheres to thecheese. In order to get good adherence it is necessary to add so much waxy material to the nlm that it is difiicult to print on the nlm with the inks ordinarily employed in this type of printing. It is desirable to use a nlm with the heavy bloom obtained when sunicient wax is used to cause a bloom on both sides, because this gives better cling to the cheese. However, the hazy outer surface is unattractive in appearance, and printing is almost impossible because of the wax on the surface. Furthermore, the sheet vwhich contains so much wax is not as .impervious to vapors and odors, etc., as an untreated' rubber hydrochloride nlm and it has been noticed that when a rubber hydrochloride nlm of high wax content is used for packagingI process cheese and the Wrapped package is enclosed in a pine box, pine vapors from the box pass through the nlm and contaminate the cheese'.

According to this invention a rubber hydrochloride film saturated with a waxy substance and having a bloom of the waxy substance thereon is -laminated to a nlm (preferably a relatively clear, rubber hydrochloride nlm) containing no wax, or substantially no wax. This composite sheet may be used for packagingl a variety of materials but is designed particularly for the packaging of process cheese. The laminated nlm is preferably nrst made into a bag with the waxcontaining nlm forming the inner surface of the bag, and the process cheese is run hot into this bag. The bag is .then sealed in the usual way. The outer ply of this bag is substantially wax free. The package thus formed may be enclosed in a cardboard carton or in a wooden box or CII may be included in any other suitable outer container.

lWhen the wax-containing nlm is formed by casting on a belt, if the rubber hydrochloride contains only a small amountof wax in excess of that which can be retained by the rubber hydrochloride, this excess will bloom out on the surface of the nlm adjacent the belt. When `a large amount of wax is used the coating formed on the surface of the nlm adjacent the belt will be heavier than that on the opposite surface.

In laminating the wax-containing film to the other nlm, it will be the surface of the waxcontaining nlm which carries no wax, or the lesser amount of wax, which will be united to the other ply of nlm.

In uniting the waxy'and non-waxy sheets it has been found desirable to apply most or all of the heat used for the lamination through the non-waxy sheet, as by passing the two sheets over a heatedroll with the non-waxy sheet in contact with the roll. This forces some of the wax from the wax-containing sheet to the outer surface of the laminated structure, thereby increasing the thickness of the wax coating on the sheet.

The non-waxy nlm may be printed, and this printing may be done before or after the lamination. If the non-waxy nlm is printed before lamination to the wax-containing nlm, the printed surface may advantageously be brought into contact with theWax-containing nlm. Such reverse printing is desirable for several reasons.

' For one thing, there is no printing on the surface of the nlm and it is therefore particularly suited for the packaging of greasy or wet foodstuns, since the printing cannot rub off or off-set onto contacting surfaces. This is a desirable method of preparing printed nlm even though the waxcontaining nlm is not saturated with a waxy substance and is free from any wax bloom.

The wax-containing nlm will preferably contain a maximum amount of wax or other waxy substance. It may, for example, contain 30 or 40 or 50%. The wax employed is preferably an amorphous, such as SS" wax made by National Wax Co., Chicago, although other waxes may be used such as Petrowax A" made by Biwax Corp., Chicago, Syncera, Cerese and beeswax.

The non-waxy nlm may be an unplasticized nlm, or it may be nlm which contains butyl stearate, dibutyl phthalate, dibutyl sebacate or other suitable plasticizeror a mixture of plasticizers. A 215% or 5% butyl stearate-contaim' ing nlm is suitable and larger amounts of plasthis invention may be the same thickness or different thicknesses. For example, the sheet of -rubber hydrochloride film sold on the market as Pliofllm NOVW which is a rubber hydrochloride film saturated with an amorphous wax and 'coated with o. bloom of wax,wh1oh nim is .0007

- inch thick, may be laminated to a sheet of Pliofilm NO which contains no plasticizer and which is also .0007 inch thick. I'he Pliofilm NOVW is formed by adding 30% of amorphous wax to a rubber hydrochloride cement (based on solids content) which may be a benzene cement. The mixture is cast into the film. On evaporation of the solvent the rubber hydrochloride is saturated with the wax and the excess wax forms a bloom on the under surface of the film adjacent the casting surface. A film of Plioillm NOVW .0007 inch thick may be laminated to a sheet .0007 inch thick of Pliofilm P-4 which is rubber hydrochloride film which contains approximately 10% 'of butyl stearate. As another example, a sheet of the said wax-containing film .0007 inch thick may be laminated to a sheet .0008 inch thick of Pliofilm N2 which is rubber hydrochloride film which contains approximately 5% of butyl stearate. Either film may, if desired, contain a photochemical inhibitor, although this is not necessary. Films of different gauges may be used and may be united to films of different composition. In fact the outer ply need not be rubber hydrochloride film. It may, for example, be a cellulosic film such as a regenerated cellulose sheet or glassine or a sheet of cellulose acetate or ethyl cellulose or other cellulose ester or ether. It may be a film of polymerized vinyl derivative such as a film of Koroseal or Vinylite or the like.-

Any other transparent film 'may be used. Adhesive maybe used for uniting the films, but

ing them together with suicient heat to unite them.

'I'he invention will be further described in oonnection with the accompanying drawing in which:

Fig. l is an elevation of an unprinted. laminated sheet of this invention;

Fig'. 2 is a printed sheet, the printing being on the non-waxy component;

Fig. 3 is an elevation of the printed sheet shown in Fig. 2; and

Fig. 4 shows a brick of process cheese wrapped inthe lm.

As shown in Fig. 1 the two plies of film are united directly without an adhesive. The one side of the composite sheet contains so much wax that there is a bloom of wax, and preferably a heavy bloom, on the surface. This is softened as the hot cheese is brought in contact with it and the cheese and film adhere to one another.

Figs. 2 and 3 illustrate the preferred way of printing such nlm. The printing is between the two films, as shown in Fig. 3. The wax bloom on the wax-containing fllm makes it unprlntable. The non-waxy film is printed and then the printed surface is united to the wax-containing film by heat and pressure.

Fig. 4 shows a package of process cheese wrapped in the film I. The wrapped cheese is put in a pine box 2. The cover is then nailed down. The wax-containing side of the composite film I is next to the cheese and the nonwaxy side of the film which is non-pervious to vapors protects the cheese from the pine vapors.

The composite sheet may be used for wrapping other materials, such as chili con carne, head cheese, cooked, spiced beef, scuse, scrapple, peanut butter, cream cheese, cheese foods, etc.

My United- States Patent 2,307,081 claims a rubber lm saturated with wax and coated on one side with a thin coating of wax and on the other side with a heavier coating of wax and also claims the process of making such a sheet by casting.

What I claim is:

The method of laminating a non-waxy rubber hydrochloride film to a wax-containing rubber hydrochloridefilm by heat and pressure to produce a laminated sheet of wax-containing rubber hydrochloride and rubber hydrochloride which is substantially wax free, which comprises supplying sufficient heat for the lamination preferably the lms are united by merely press- /through the non-waxy film to force some wax 

